The intense commercialization of metallocene polyolefin catalysts (metallocene being cyclopentadienyl based transition metal catalyst compounds) has led to widespread interest in the design of metallocene and non-metallocene, homogeneous catalysts, particularly for use in the economical gas and slurry phase processes. This field is more than an academic curiosity as new catalysts in gas or slurry phase may provide an easier, more economical pathway to currently available products and may also provide product and process opportunities which are beyond the capability of metallocene catalysts in the gas or slurry phase.
New catalysts, however, are not automatically useable in polymerization process, particularly a gas phase polymerization process. Some catalysts are too active for the gas phase and foul the reactor. Other catalysts cannot be supported and thus are difficult to introduced into the reactor in such as way that fouling does not occur.
There is also a drive in the art to develop more and more economical processes to produce what are traditionally called bi-modal polymers. These polymers typically show large concentrations of two or more polymer species on a Gel Permeation Chromatograph. (For our purposes, peaks and shoulders are thought to represent distinct species). These polymers are sought after because they can address several needs of individual industries at once. For example, in the film blowing industry, a polymer comprising a high molecular weight species that provides strength and a low molecular weight species that provides processability is highly desired. Blends of these two types of polymers tend to separate or have other miscibility problems. But polymers produced in one reactor having two or more molecular weight species do not have these problems to the same extent if at all. Typically these multimodal polymers are made by using two different catalysts in the same reactor or in a series of reactors. Thus, there is a desire in the art to produce new and more improved methods to obtain such multi-modal polymers and to make the production process more efficient.
Schrock et al in U.S. Pat. No. 5,889,128 discloses a process for the living polymerization of olefins in solution using initiators having a metal atom and a ligand having two group 15 atoms and a group 16 atom or three group 15 atoms. In particular, the solution phase polymerization of ethylene using {[NON]ZrMe}[MeB(C6F5)3] or {[NON]ZrMe(PhNMe2)]}[B(C6F5)4] is disclosed in examples 9 and 10.
EP 893 454 A1 discloses unsupported transition metal amide compounds used in combination with activators to polymerize olefins in the solution phase.
Mitsui Chemicals, Inc. in EP 0 893 454 A1 discloses transition metal amides combined with activators to polymerize olefins.
EP 0 874 005 A1 discloses phenoxide compounds with an imine substituent for use as a polymerization catalyst.
EP 893 454 A1 discloses unsupported transition metal amide compounds used in combination with activators to polymerize olefins in the solution phase.
U.S. Ser. No. 09/312,878 filed May 17, 1999 discloses a gas or slurry phase polymerization process using a supported bisamide catalyst.
Japanese Abstract JP 10330416A appears to disclose transition metal amide catalysts in combination with Ziegler-Natta catalysts. Japanese Abstract JP 10330412A appears to disclose transition metal amide catalysts in combination with group 4 transition metal cyclopentadienyl catalysts.
Ethylenebis(salicylideneiminato)zirconium dichloride combined with methyl alumoxane deposited on a support and unsupported versions were used to polymerize ethylene by Repo et al in Macromolecules 1997, 30, 171-175.
U.S. Pat. Nos. 5,672,669, 674,795 and EP 0 668 295 B1 disclose spray dried filled metallocene catalyst compositions for use in gas phase polymerizations.